In the 3rd Generation Partnership Project (3GPP), a radio access method and a radio network for cellular mobile communications (hereinafter referred to as “Long Term Evolution (LTE)”, or “Evolved Universal Terrestrial Radio Access (EUTRA)”) have been considered. In LTE, a base station device is also referred to as an evolved NodeB (eNodeB), and a mobile station device is also referred to as user equipment (UE). LTE is a cellular communication system in which an area is divided into a plurality of cells to form a cellular pattern, each of the cells being served by a base station device. A single base station device may manage a plurality of cells.
LTE supports a time division duplex (TDD). LTE that employs a TDD scheme is also referred to as TD-LTE or LTE TDD. TDD is a technology that enables full duplex communication in a single frequency band by performing time division multiplexing on an uplink signal and a downlink signal.
In the 3GPP, application of a traffic adaptation technology and an interference reduction technology (DL-UL interference management and traffic adaptation) to TD-LTE has been studied. The traffic adaptation technology is configured to enable a ratio of an uplink resource to a downlink resource to change depending on uplink traffic and downlink traffic. The traffic adaptation technology is also referred to as dynamic TDD.
In NPL 1, a method of using a flexible subframe is disclosed as a method of realizing traffic adaptation. The base station device can receive an uplink signal or transmit a downlink signal in the flexible subframe. In NPL 1, as long as the base station device does not instruct the mobile station device to transmit the uplink signal in the flexible subframe, the mobile station device regards the flexible subframe as a downlink subframe.
NPL 1 discloses that hybrid automatic repeat request (HARQ) timing for a physical downlink shared channel (PDSCH) is determined on the basis of newly introduced uplink-downlink configuration, and the HARQ timing for a physical uplink shared channel (PUSCH) is determined on the basis of the first UL-DL configuration.
NPL 2 discloses that (a) a UL/DL reference configuration is introduced and that (b) several subframes are possibly scheduled, for either of uplink and downlink, by dynamic grant/assignment from a scheduler.
In Section 7.2 in NPL 3, a procedure performed by the mobile station device for reporting channel state information (CSI) is disclosed. The base station device allocates a downlink resource to the mobile station device on the basis of the channel state information reported from a plurality of mobile station devices. The channel state information includes a channel quality indicator (CQI).